use OpiloClient\Configs\Account;
use OpiloClient\Configs\ConnectionConfig;
use OpiloClient\V2\HttpClient;
...
$config = new ConnectionConfig('http://bpanel.opilo.com');
$account = new Account('YOUR_WEBSERVICE_USERNAME'), 'YOUR_WEBSERVICE_PASSWORD');
$client = new HttpClient($config, $account);

use OpiloClient\Request\OutgoingSMS;
...
$message = new OutgoingSMS('3000****', '0912*******', 'Hello World!');
$responses = $client->sendSMS($message);

$messages = [
    new OutgoingSMS('3000****', '0912*******', 'Hello World!'),
    new OutgoingSMS('3000****', '0912*******', 'Hello World!'),
];
$response = $client->sendSMS($messages);

use OpiloClient\Response\SMSId;
use OpiloClient\Response\SendError;
...
for ($i = 0; $i < count($response); $i++) {
    if ($response[$i] instanceof SMSId) {
        //store $response[$i]->id as the id of $messages[$i] in your database and schedule for checking status if needed
    } else //$response[$i] instanceof SendError {
        //It could be that you run out of credit, the line number is invalid, or the receiver number is invalid.
        //To find out more examine $response[$i]->error and compare it against constants in SendError class
    }
}

$minId = 0;
while (true) {
    $inbox = $client->checkInbox($minId);
    $messages = $inbox->getMessages();
    if (count($messages)) {
        foreach ($messages as $message) {
            //Process $message->opiloId(), $message->getFrom(), $message->getTo(), $message->getText(), and $message->getReceivedAt() and store them in your database
            $minId = max($minId, $message->getOpiloId() + 1);
        }
    } else {
        //no new SMS
        //Store $minId in your database for later use of this while loop! You don't need to start from 0 tomorrow!
        break;
    }
}

$opiloIds = $yourDatabaseRepository->getArrayOfOpiloIdsOfMessagesSentViaSendSMSFunction();
$response = $client->checkStatus($opiloIds);
foreach ($response->getStatusArray() as $opiloId => $status) {
    //process and store the status code $status->getCode() for the SMS with Id $opiloId
    //Take a look at constants in OpiloClient\Response\Status class and their meanings
}

$numberOfSMSYouCanSendBeforeNeedToCharge = $client->getCredit()->getSmsPageCount();

use OpiloClient\Response\CommunicationException;
...
try {
    ...
    $client->sendSMS(...);
    ...
} catch (CommunicationException $e) {
    //process the exception by comparing $e->getCode() against constants defined in CommunicationException class.
}